The outer layer of skin surrounding the body performs an important protective function as a barrier to infection and as a means of regulating the exchange of heat, fluid and gas between the body and external environment. Where the skin is removed or damaged by being abraded, burnt or lacerated, this protective function is diminished. Such areas of damaged skin are therefore conventionally protected by the application of a wound dressing which serves as a skin substitute.
Examples of wound dressings which have been developed are hydrocolloid dressings. UK Patent Number 1471013 and Catania et al U.S. Pat. No. 3,969,498 describe hydrocolloid dressings which are plasma soluble, which form an artificial eschar with the moist elements at the wound site, and which gradually dissolve to release medicaments. These dressings comprise a hydrophilic foam of dextran polymer which can be applied without inunction, is non-irritating to the lesion and is easily removed.
Known hydrocolloid dressings in general, and the Catania dressings in particular, are however subject to a number of drawbacks. The major disadvantages of these dressings are that they disintegrate in the presence of excess fluid at the wound site and that they have little if any control over water loss from the wound. This latter disadvantage is particularly important as excess water loss from a wound will cause an increase in heat loss from the body as a whole, potentially leading to hypermetabolism.
In addition, such hydrocolloid dressings as are known require frequent dressing changes. This is especially true of the Catania dressing due to the dissolution of the dextran polymer at the wound site by the fluid lost through the wound in the exudative stage.
New Zealand Patent Specification Number 198344 discloses a bandage which contains a medicament that is administered topically to the skin of a patient. The bandage disclosed comprises a backing element and a self-adhesive matrix, which matrix in turn comprises a solid phase and a liquid phase with the medicament being molecularly dispersed in the matrix. While the solid phase of the matrix can comprise synthetic polymers and natural gums, no teaching is provided of a synthetic skin substitute which can consist of only a natural or synthetic polymer, a non-gellable polysaccharide and a cross-linking agent.
It is an object of the present invention to go some way towards overcoming the above disadvantages or at least to provide the public with a useful choice.